5 things to know about marijuana in the U.S.

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'Inside Man' looks at medical marijuana

Story highlights

Two states have made pot completely legal; 18 allow medical marijuana use

But it's still illegal under federal law; gap growing between state and federal laws

Studies, personal stories attest to medical value of marijuana

New tax revenues in states that legalized pot have fallen short of predictions

There appears to be a shift in the United States in favor of relaxing marijuana laws. Making pot legal, supporters say, can simultaneously provide relief for the sick and poke a hole in the operations of drug cartels. But the federal government has not acted to remove marijuana's label as a controlled substance and has reaffirmed its anti-pot policy.

Morgan Spurlock's new program, "Inside Man," premieres on CNN this weekend with an in-depth look at the medical marijuana business in California. Here are five things to know about the current debate over the drug:

There is evidence of changing attitudes in America

Public perceptions about pot have come a long way in the past decades, from the dire warnings of "Reefer Madness" to growing acceptance of medical marijuana use.

Laws in several states decriminalizing marijuana or allowing for medical marijuana use are one indicator of how voters feel.

The financial gains in Washington and Colorado, the two states that have legalized marijuana, have not been as great as some expected.

Washington had projected up to $450 million in added annual tax revenue, but the state's new pot consultant figures it could be little more than half that.

In Colorado, the Colorado Futures Center think tank forecasts $130 million in new tax revenue but thinks that won't even cover the cost of regulating the new industry.

Still, some say the legalization of pot would bring down the black markets that have left a murderous trail, drawing parallels with what happened during and after the prohibition of alcohol in the 1920s and '30s.

Estimates vary widely on how big a hit drug cartels would take if marijuana were legalized. While U.S. officials said in 2009 that 60% of cartel revenue came from weed, the RAND Corp. said the following year that "15-26 percent is a more credible range."

A report this month by the Mexican Competitiveness Institute predicted Mexican drug organizations, specifically the Sinaloa Cartel, could lose almost $2.8 billion just from the legalization votes in Colorado and Washington.

Opponents, however, say that science has yet to prove that marijuana is safe.

A series of trials published by the University of California Center for Medicinal Cannabis Research last year showed cannabis can help patients suffering from neuropathic pain, commonly caused by degenerative diseases like multiple sclerosis or fibromyalgia. Neuropathic pain is also a common side effect of chemotherapy and radiation.

Study participants on cannabis reported a 34% to 40% decrease in pain, compared with the 17% to 20% decrease seen in patients on a placebo drug.

The National Institute on Drug Abuse, meanwhile, says that marijuana causes an increase in heart rate, which could put users at risk for a heart attack or stroke. Marijuana smoke also contains carcinogens similar to those in tobacco smoke.

Jason David, whose son Jayden suffers from seizures, turned to the drug and calls it "miracle marijuana."

Jayden has Dravet syndrome, a rare and catastrophic form of childhood epilepsy. The boy started taking a liquid, nonpsychoactive form of marijuana, which his father says controls his violent seizures. This form ensures that Jayden does not get high from the drug, his father says, but has allowed him to enjoy the things other boys do.

Spurlock said he imagined that marijuana dispensaries -- the places where patients can purchase medical pot -- would be shady places. What he found at Harborside Health Center, the largest dispensary in the country, surprised him.

The space was large and clean, nicer than many health clinics he has been to, Spurlock said. Tight security regulated who could enter the business, which sells various strains of marijuana and lotions, pills and other products derived from the drug.

Some strains of marijuana are known to be more cerebral and energizing, while others are more sedative in nature and have greater pain-relieving properties. Dispensaries such as Harborside categorize their products accordingly and have specific strains for different ailments.

Marijuana laws put state and federal statutes at odds

Eighteen states have either decriminalized or allowed medical marijuana in some fashion. While the state laws have allowed dispensaries to open, they remain illegal under federal law. The gap between state and federal laws is widening when it comes to marijuana enforcement.

For instance, state law makes it legal to possess marijuana in Washington state, but selling drugs is still a federal crime. There is a similar situation in California, where medical marijuana is allowed, but again, growers don't have the same legal protections that users have.

"So I'm not sure where you're supposed to get it," King County Prosecutor Dan Satterberg said when the law went into effect. "If you stumble across some on the street or it falls from the sky, then you can have it. Otherwise, you are part of a criminal chain of distribution."

In 1996, California voters approved Proposition 215 to exempt doctors and seriously ill patients from marijuana laws and allow them to grow and use it in treatment. But government crackdowns on growers since then have led to multiple lawsuits.

Harborside, the dispensary that Spurlock visited, is fighting to remain open amid efforts by the feds to shut it down.